Effects of Nitrogen Application on Soil Nitrificati on and Denitrification Rates and N 2 O Emissions in Greenhouse

Abstract

Nitrous oxide (N 2 O) has significant impact on global warming and lea ds to the depletion of ozone in the stratosphere. Agricultural soil is regarded as a major source of N 2 O emissions. In recent years, greenhouse grown vegeta bles have rapidly developed in China. Although excessive fertilizer application in greenh ouse vegetable production can result in increased N 2 O emissions, research data on such emissions from g reenhouse vegetables, such as cucumber, remains limited. In this study, f our nitrogen (N) fertilizer treatments including 1,200 (N 1200 , traditional N amount), 900 (N 900 ), and 600 kg N ha -1 (N 600 ) and the control (N 0 ) were carried out on cucumber in a greenhouse in t he North China Plain. Results showed that N 2 O emissions mainly occurred in the first five days after topdressing, and accounted for 75.8% -95.2% of total N 2 O emissions produced in the whole interval (10 days). Significant exponential c orrelations were observed between N 2 O flux and nitrification or denitrification rates ( P < 0.01). The results also indicated that nitrification dominated and played a more important role in N 2 O emissions than denitrification under the irrigation conditions of the study (water-filled pore space was 40.0 to 66.6%). Cumulative N 2 O emissions were 0.48-5.01 kg N ha -1 in the cucumber growing season, accounting for 0.28-0.38% of nitrog en input. Compared to N 1200 , treatment N 600 significantly reduced the rate of N 2 O emissions by 53.4%, and also maintained cucumber yield. Based on this study, 50% of the traditional N fertilizer rate (N 600 ) was considered sustainable for greenhouse cucumbe r production in the North China Plain. Keywords: Cucumber, Environmental factor, Nitrogen fertilizer , N 2 O flux. Soil NO3 - N.